Setting the frequency of a clock pendulum by optical mechanical deformation

Abstract

The invention relates to a method for precisely regulating the speed of a mechanical pendulum with a pendulum inertia mass, which in a first step is equipped with an actuator made of a material adapted to undergo irreversible local microswelling under the action of laser irradiation, in order to impart radial movement to the inertia mass during appropriate laser irradiation on a writing zone of the actuator, in a second step, the initial speed of the pendulum is set and measured, in a third step, the direction and value of the deviation required to achieve a predetermined speed range, and the direction and value of the stroke to be imparted to the inertia mass are calculated, in a fourth step, the writing zone is subjected to femtosecond laser irradiation in order to generate a swelling line by local molecular swelling, thus deforming the actuator radially, in a fifth step, the speed is measured, and if necessary, the third and fourth steps are repeated.

Description

TECHNICAL FIELD

[0001] The invention relates to a method for precisely regulating the rate of a mechanical timepiece balance, the balance comprising at least one inertial mass arranged to oscillate about an axis of rotation and returned to a rest position by elastic return means.

[0002] The invention also relates to a mechanical timepiece balance adapted to implement this method.

[0003] The invention also relates to a timepiece, in particular a watch, comprising such a mechanical timepiece balance.

[0004] The invention relates to the field of rate setting of a mechanical timepiece balance, in particular a balance already assembled into a watch head. BACKGROUND

[0005] Modifying the frequency of a mechanical balance almost always involves a change in the stiffness of the elastic parts, in particular the hairspring, or in its inertia / mass. For example, in a hairspring balance of a mechanical watch, it is common to find devices for regulating the stiffness of the balance spring, such as by moving a pin to change its effective length. Another method commonly used is to modify the inertia of the balance by moving a small mass, such as a screw or a biased rotating inertia block, towards the outside or inside of the balance.

[0006] However, these operations require opening the watch and removing the movement, which tends to distort the results once the watch case is closed again, with deviations of up to 10 seconds per day, which is troublesome for movements that need to be set based on 0 to + 2 seconds per day. Furthermore, these precision mechanisms often cause mechanical play once the setting tool (the force used for setting) is removed, resulting in deviations. SUMMARY

[0007] The invention aims to precisely regulate the frequency of a mechanical timepiece balance, for example a watch hairspring balance, without having to disassemble the watch (or more generally, the timepiece) with this balance.

[0008] To this end, according to the invention, the invention relates to a method for precisely regulating the rate of a mechanical timepiece balance.

[0009] The invention also relates to a mechanical timepiece balance adapted to implement this method.

[0010] The invention also relates to a timepiece, in particular a watch, comprising such a mechanical timepiece balance. BRIEF DESCRIPTION OF DRAWINGS

[0011] The objectives, advantages and features of the invention will become more apparent upon reading the following detailed description, and upon reference to the accompanying drawings, in which:

[0012] -Figure 1 A table is schematically represented in plan view, with a table head comprising a transmissive transparent element separating the exterior and the interior of the table. This transmissive transparent element, represented here in the form of the back of the table, enables the user and the light source to optically access all or part of the table oscillator, here a hairspring balance, represented here with only the balance wheel, without the balance wheel spring, so as not to overcomplicate the drawing. Figure 1 The incident laser beam meeting the balance wheel is represented in dotted line;

[0013] - Figure 2 A detailed view of a balance wheel according to the application is schematically represented in plan view as Figure 1 The balance wheel comprises, from its rim to the transmissive transparent element, a plurality of supports, arranged in pairs symmetrically with respect to the rotation axis of the balance wheel. Each of these supports supports, on the side of the transmissive transparent element, at least one inertia mass, which is movable radially with respect to the rotation axis of the balance wheel. The drawing shows, for each support, three different positions of such an inertia mass, the intermediate hatching being the intermediate position between the two end positions marked in dotted line;

[0014] - Figure 3 The balance wheel in Figure 2 is represented in cross section perpendicular to the transmissive transparent element, separating on the one hand, at the top of the drawing, the external environment in which at least one laser source is located, and on the other hand, at the bottom of the drawing, the interior of the table case containing the balance wheel. The drawing shows the rim carrying the supports supporting, on the side of the transmissive transparent element, such an inertia mass, which is movable radially with respect to the rotation axis of the balance wheel under the action of the light beam emitted by the laser source. The drawing is centred on the inertia mass represented in hatching, and shows another radial position of this inertia mass, represented in dotted line;

[0015] - Figure 4 is a graph showing on the y axis the rate deviation in seconds per day, on the x axis the symmetrical radial movement value of the two inertia masses in microns, and superimposed the results obtained for four inertia mass values from 1.20 mg to 2.40 mg;

[0016] - Figure 5 The implementation principle of an optical mechanical actuator for moving an inertia mass is schematically represented in plan view: the support carries a fastener, one of which carries the optical mechanical actuator itself, which comprises two parallel arms forming a U shape when they are connected at the ends by a common segment, the first arm extending between the fastener of the support and the common segment, the second arm extending between the common segment and the exit point, here formed by the neck of an amplification mechanism, for amplifying the exit stroke of the optical mechanical actuator, to provide sufficient stroke for the inertia mass;

[0017] Figure 6 is schematically shown in plan view Figure 5 another alternative embodiment of the optical mechanical actuator of the

[0018] - Figure 7 is schematically shown the case of pulsed etching of the writing zone of the second arm, at the top of the figure, in the thrust movement of the inertia block, the overall movement of the exit point is then on the left of the figure;

[0019] - Figure 8 is schematically shown the case, opposite to that of Figure 7 , in which the writing zone of the first arm is pulsed etched, at the bottom of the figure, in the retraction movement of the inertia block, the overall movement of the exit point is then on the right of the figure;

[0020] - similar to Figures 5 to 8 , Figure 9 is shown an alternative embodiment in which the inertia block and the corresponding support are formed in a single layer by a chip, the support is then constrained to a fastening zone for fastening on the balance wheel; this alternative embodiment is particularly suitable for applying the invention to the specific case of a balance wheel of diameter 10.6 mm, carrying a 2x2 mm chip, comprising a support and an inertia block;

[0021] - similar to Figure 3 , Figure 10 is shown a plan view of a balance wheel according to Figure 9 equipped with two chips;

[0022] - Figure 11 is a schematic cross-sectional view through the rotation axis of the balance wheel, which shows the rim of the balance wheel (carrying the support), the inertia block (not shown), the emission writing laser source for writing on the writing zone, and the detection laser obliquely mounted on the left of the figure, in which the light beam reflected by the balance wheel and the elements included therein is collected at the right of the figure by a collection device such as a photodetector;

[0023] - Figure 12 is schematically shown in plan view a detailed view of the arrangement according to Figure 11 , with a laser writing source and a laser detection source, for the case of balance wheel swing, and in which the laser irradiation is synchronized with its angular position; the figure represents a portion of the balance wheel rim, which carries the arrangement according to Figure 9 ​is a chip; the arcs in dotted line correspond to the instantaneous position of the laser writing source, which illuminates perpendicularly to the plane of the figure, and which can therefore in this case write in the writing zone of the first lower arm, to generate in this writing zone a molecular dilation represented by the small arrows, the adjacent small arrows corresponding to writings performed also in the same zone along the x of the writing source, corresponding to different beams with respect to the pivot rotation axis; at the bottom of the figure, from left to right, one can see the laser detection source, the converging lens, the incident beam to the pivot, the reflection point on the pivot or on the organ it carries, the reflected beam, the converging lens and the photodetector;

[0024] - Figure 13 The three time graphs are juxtaposed, drawn with different time scales on the x axis, but arranged in relation to each other to show the specific times and phenomena that occur: the upper graph shows on the y axis the angular speed omega OME of the pivot, the middle graph shows on the y axis the value of the photodetector signal VPD, while the lower graph shows on the y axis the light intensity IIE emitted by the laser writing source;

[0025] - Figure 14 is a block diagram showing the connections between the control device, the worktable with cross motion for handling the writing laser, the writing laser, the detection laser, the device for collecting the reflected beam and the device for starting and stopping the swing;

[0026] - Figure 15 is a block diagram comprising a block diagram of the five main steps of the rate adjustment method according to the invention. DETAILED DESCRIPTION

[0027] The present invention proposes to induce a permanent mechanical tension, and thus a volume dilation, in a flexible microstructure machined in a glass (fused silica) or similar support, in particular by femtosecond laser excitation.

[0028] The support is embedded on the inertial mass of the swing of a mechanical watch, in particular on the balance. The movement of a part of the mechanism will change the inertia of this inertial mass and thus the frequency of the swing, in particular of the hairspring balance. As seen in the article "Non-contact sub-nanometer optical repositioning with femtosecond lasers" by Y. Bellouard, Optics Express, November 2, 2015, volume 23, number 22, by writing parallel internal tension dilation lines, movements of the order of several microns can be obtained in such a glass microstructure.

[0029] The microstructure itself is realized by a punching method with an accuracy of + / - 1 micron and using the same type of laser, followed by a chemical etching, as in the above cited article, or as in the article "Fabrication of high aspect ratio microfluidic channels and tunnels using femtosecond laser pulses and chemical etching" by Y. Bellouard et al. in Optics Express, vol. 12, pages 2120-2129, 2004, or as seen on the website of FEMTOprint SA, 6933 Muzzano (CH) at the address https: / / www.femtoprint.ch / devices-photos.

[0030] The absence of a pivot or any other frictional guiding device ensures a high positioning accuracy and zero hysteresis. For the laser wavelength, the light excitation passes directly through the table glass or any non-absorbing shell spacing, or is defocused at the passage point.

[0031] The invention is more particularly but not limitatively described for the case where the oscillator is a table oscillator and is a hairspring balance.

[0032] The invention relates to a method for precisely regulating the rate of a mechanical watch oscillator 100 comprising at least one inertial mass 1 arranged to oscillate about an axis of rotation D and returned to a rest position by elastic return means.

[0033] According to the invention, as Figure 15 shown in a first step 801, the oscillator 100 is equipped with at least one inertial mass 1 comprising an actuator 35 made of a material suitable for undergoing irreversible local microswelling under the action of a laser irradiation. This actuator 35 is arranged to impart to the inertial mass 3 a radial linear stroke with respect to the axis of rotation D, directly or with the aid of at least one stroke amplifier 36, when a writing zone 39 included in the actuator 35, or more particularly a first writing zone 391 on the first arm 33, or a second writing zone 392 on the second arm 34, is subjected to a suitable laser irradiation. As will be seen hereinafter, each writing zone 39, 391, 392 is able to receive a swelling line 390 by laser writing.

[0034] The description "writing zone 39" relates to the general case, the terms "first writing zone 391" and "second writing zone 392" relating to a preferred but non-limiting application on the first arm 33 and on the second arm 34 of the inertial mass 3, respectively.

[0035] More specifically, when the inertial mass 1, which extends on either side of the rotation axis D, is subjected to a rotational movement, it is equipped with at least one pair of diametrically opposed actuators 35 made of a material adapted to undergo irreversible local microswelling under the action of a laser irradiation. This is particularly true when the inertial mass 1 is a balance of a balance wheel type oscillator.

[0036] More specifically, when the inertial mass 1 is suspended with respect to the rotation axis D, like an inertial mass suspended by a flexible bar, it is symmetrical with respect to a plane passing through the rotation axis D, the inertial mass 1 being equipped with at least one pair of symmetrical actuators 35 with respect to this plane of symmetry.

[0037] More specifically, the method is applicable to an oscillator 100 having at least two inertial masses 1, each comprising such an actuator 35.

[0038] In a second step 802, a first particularly rough setting of the initial rate of the oscillator 100 is performed in a first rate range and this rate is measured.

[0039] In a third step 803, the direction and value of the rate deviation to be imparted to the oscillator 100 so that it enters a predetermined second rate range are calculated, and the direction and value of the stroke to be applied to each of the inertial masses 3 included in the oscillator 100 are calculated.

[0040] In a fourth step 804, at least one writing zone 39, 391, 392 is subjected to a femtosecond laser irradiation, at least one swelling line 390 being created by local molecular swelling of the material, causing the actuator 35 to deform radially with respect to the rotation axis D.

[0041] In a fifth step 805, the rate of the oscillator 100 is measured, and if necessary, the third step 803 and the fourth step 804 are repeated until the rate of the oscillator 100 is in the predetermined second rate range.

[0042] More specifically, during the fourth step 804, a femtosecond laser source 700 is used, which is mounted on a worktable having a cross movement 710 or a radial stroke, in order to add different series of irradiations on different beams with respect to the rotation axis D, so as to create a series of swelling lines 390 in positions close to each other.

[0043] More specifically, during the fourth step 804, the femtosecond laser source 700 is used to perform irradiations in each direction of rotation of the inertial mass 1.

[0044] More specifically, during the fourth step 804, the control device 790 is used to control the irradiation of the femtosecond laser source 700 as a function of the information on the presence or absence of material provided by the detection laser 750 and the combination of collection means 760 or photodetectors.

[0045] More particularly, during the first step 801, the actuator 35 is chosen to comprise a first writing zone 391 on the first arm 33, and a second writing zone 392 on the second arm 34, parallel to the first arm 33 along the radial linear direction L and joined thereto at a common segment 334. The actuator 35 is thus mounted in an "S" shape between, on the one hand, a fastening zone 30 fastened to a support 2 mounted on the inertial mass 1 or directly to the inertial mass 1, and, on the other hand, an exit point or coupling neck 32 for coupling with the amplification mechanism 36. The actuator 35 is arranged to act in two opposite directions along the linear direction L, whereby, during the fourth step 804, for a gain setting, the laser shot writing occurs in the first writing zone 391 on the first arm 33, or, for a loss setting, in the second writing zone 392 on the second arm 34.

[0046] More particularly, during the first step 801, the actuator 35 is chosen to comprise an exit point or coupling neck 32 for coupling with the amplification mechanism 36, the amplification mechanism being arranged to amplify the exit stroke of the actuator 35, to impart an amplified stroke to the inertial mass 3.

[0047] More particularly, the amplifier 36 is a parallelogram and comprises a linkage system with links 310 arranged between the flexible necks 31, forming a linear guide along the radial linear direction L.

[0048] More particularly, during the first step 801, the actuator 35 is chosen to comprise a fastening zone 30 rigidly connected to a support 2 mounted on the inertial mass 1. And the support 2 forms a single-piece assembly forming a flexible micro-mechanism in which the actuator 35, the amplifier 36 and the inertial mass 3 are mounted in series with one another.

[0049] More particularly, during the first step 801, the actuator 35 is chosen to comprise a fastening zone 30 fastened to a support 2 mounted on the inertial mass 1 or rigidly connected to the support 2, and the actuator 35 and / or the support 2 are made of glass.

[0050] More particularly, during the first step 801, the inertial mass 1 is chosen in the form of a balance comprising at least one pair of identical inertial masses 3, diametrically opposite with respect to the rotation axis D.

[0051] More particularly, during the first step 801, the pendulum 100 is incorporated into a watch head 500 of a watch 1000, said watch head 500 comprising at least one transmissive transparent element 600 separating the exterior and the interior of the watch 1000 and enabling optical access to at least the inertial mass 1 of the pendulum 100 of the watch.

[0052] In a static alternative embodiment, during the first step 801, the rocker 100 is equipped with a stop device or a seconds device arranged to exert a pressure on the inertial mass 1 and the fourth step 804 is performed in the locked position of the inertial mass 1.

[0053] In a dynamic alternative embodiment, during the fourth step 804, the femtosecond laser writing irradiation is performed during the swing of the inertial mass 1, with angular position and irradiation synchronization.

[0054] More particularly, during the fourth step 804, the irradiation is performed with a femtosecond laser, for example but not limited to a wavelength between 900 nm and 1100 nm, a pulse time between 200 fs and 350 fs, a pulse energy of the order of 200 nJ to 300 nJ, a repetition frequency of 700 kHz to 900 kHz. It is clear that different femtosecond lasers (wavelength, pulse time and energy) can be used, as long as it can modify the material as described above.

[0055] The application also relates to a mechanical timepiece rocker 100 comprising at least one inertial mass 1 arranged to swing about a rotation axis D and to return to a rest position by elastic return means, the rocker being adapted to the implementation of the method. According to the application, the at least one inertial mass 1 comprises an actuator 35 made of a material adapted to undergo an irreversible local microswelling under the action of a laser irradiation. The actuator 35 is arranged to impart, directly or by means of at least one stroke amplifier 36, a radial linear stroke of the inertial mass 3 relative to the rotation axis D when the writing zone 39, 391, 392 comprised in the actuator 35 is subjected to a suitable laser irradiation.

[0056] More particularly, the actuator 35 comprises a first writing zone 391 on the first arm 33 and a second writing zone 392 on the second arm 34 parallel to the first arm 33 along a radial linear direction L and joining it at a common segment 334, the actuator 35 thus being mounted in an "S" shape between, on the one hand, a fastening zone 30 fastened to a support 2 mounted on the inertial mass 1 or directly to the inertial mass 1 and, on the other hand, an exit point or coupling neck 32 for coupling with the amplification mechanism 36, the actuator 35 being arranged to act in two opposite directions along the linear direction L, whereby, for a gain setting, the femtosecond laser irradiation is applied in the first writing zone 391 on the first arm 33 or, for a loss setting, in the second writing zone 392 on the second arm 34.

[0057] More specifically, the actuator 35 comprises an exit point of the coupling neck 32 for coupling with an amplification mechanism 36 arranged to amplify the exit stroke of the actuator 35 to impart an amplified stroke to the inertial mass 3. And the amplifier 36 is of parallelogram type and comprises a linkage system with links 310 arranged between the flexible necks 31, the links 310 forming a linear guide along a radial linear direction L.

[0058] More specifically, the actuator 35 comprises a fastening zone 30 rigidly connected to a support 2 mounted on the inertial mass 1, and the support 2 forms a single-piece assembly forming a flexible micromechanism in which the actuator 35, the amplifier 36 and the inertial mass 3 are mounted in series with each other.

[0059] More specifically, the actuator 35 comprises a fastening zone 30 rigidly connected to a support 2 mounted on the inertial mass 1, and the support 2 forms a single-piece assembly forming a flexible micromechanism in which the actuator 35, the amplifier 36 and the inertial mass 3 are mounted in series with each other.

[0060] More specifically, the actuator 35 comprises a fastening zone 30 rigidly connected to a support 2 mounted on the inertial mass 1, and the support 2 forms a single-piece assembly forming a flexible micromechanism in which the actuator 35, the amplifier 36 and the inertial mass 3 are mounted in series with each other.

[0061] The application also relates to a timepiece, in particular a watch 1000, comprising at least one such mechanical watch balance 100. According to the application, the watch 1000 comprises a watch head 500 comprising at least one transmissive transparent element 600 separating the exterior and the interior of the watch 1000 and enabling optical access to at least the inertial mass 1 of the balance 100 of the watch.

[0062] The figures show non-limiting embodiments of the application, in particular cases in which the inertial mass 1 is a balance.

[0063] Figure 1 A timepiece 1000, in particular a watch, is shown with a watch head 500 comprising a transmissive transparent element 600, such as a watch back, a watch glass or other element, separating the exterior and the interior of the watch. This transmissive transparent element 600 enables optical access to all or part of the balance 100 of the watch, and in this case at least the balance 1, the balance spring not being shown in order not to clutter the figures. This Figure 1 The incident laser beam RL meeting the balance 1 is shown in dotted line.

[0064] The present invention proposes to precisely adjust the frequency of the balance spring by means of a focused laser beam, by means of an at least partially transparent or low light absorption shell, such as the transmissive transparent element 600. The balance 100 is either already set to approximately + / - 15 seconds / day, for example using a screw not shown, or is in particular paired with a suitable balance spring in this range. By means of the movement of the small inertia mass towards the outside or inside of the balance 1, the action of the laser makes it possible to precisely set to approximately 0-2 seconds / day, to modify its inertia and thus the frequency of the balance, and thus to precisely adjust the rate of the watch.

[0065] Figure 2 A detailed view of the balance 1 according to the invention is shown in plan view as Figure 1 The balance 1 comprises, from its rim 19 to the transmissive transparent element 600, a plurality of supports 2 arranged in pairs symmetrically with respect to the axis of rotation D of the balance. These supports 2, in particular the chips, each support at least one inertia mass 3 on the side of the transmissive transparent element 600, which is movable radially with respect to the axis of rotation D of the balance 1. For each support 2, Figure 2 Three different positions of such an inertia mass 3 are shown, the intermediate hatching representing an intermediate position between the two end positions marked with dotted lines, at a radial distance X from the intermediate position. This limited number of radial positions of the inertia mass 3 is merely a particular case for the sake of clarity of the drawing.

[0066] The drawing shows a particular alternative embodiment, each support 2 being mounted on the balance 1 for ease of implementation; another alternative embodiment is possible in which the supports 2 and the balance 1 form a single-piece assembly, although the production costs are higher.

[0067] Figure 3 For a cross section perpendicular to the transmissive transparent element 600, which separates on the one hand, at the top of the drawing, the outside environment in which at least one laser source 700 is located, and on the other hand, at the bottom of the drawing, the inside part of the watch case containing the balance 1. The balance 1 comprises, from its rim 19 to the transmissive transparent element 600, a plurality of supports 2 arranged in pairs symmetrically with respect to the axis of rotation D of the balance. These supports 2 each support at least one inertia mass 3 on the side of the transmissive transparent element 600, which is movable radially with respect to the axis of rotation D of the balance 1 under the action of the beam emitted by the laser source 700. Figure 3 The inertia mass 3 is centered with hatching, and another radial position of this inertia mass 3 is shown with dotted lines. The inertia mass 3 is thus rigidly connected to the support 2, which in turn is fastened to the rim 19 of the balance 1 towards the outside of the balance 1, as shown.

[0068] The amplitude of movement depends on several laser exposure parameters. This amplitude can be controlled very precisely and the inertial mass 3 remains in place after exposure and it is possible to move the inertial mass 3 in both directions for a fixed number of cycles. In order not to destroy the unbalance, it is necessary to group the supports 2 into pairs of symmetrically opposite and it is necessary to set them simultaneously at the same amplitude. Figure 2 and Figure 3 The simplest case is shown with a pair of supports 2. Another alternative embodiment comprises the provision of an even number 2N of supports 2, N being an integer ranging from 1 to generally 10 and depending in particular on the diameter of the balance wheel 1 and the geometry of the possibility of pairing these supports 2. In this configuration with a plurality of supports 2, not only the frequency but also the unbalance can be set.

[0069] For the particular simple case of two radially opposite supports 2 shown in the figure, the relationship between the rate deviation of the pendulum 100 (deviation from the ideal frequency) in seconds / day and the radial movement X of the two inertial masses 3 in meters is given by the following equation:

[0070] - rate deviation ,

[0071] - where R is the value of the neutral rotation radius of the inertial mass 3 in meters, Io is the basic inertia of the balance wheel without inertial mass in kg*m 2 and m is the mass of the inertial mass in kg.

[0072] Figure 4 The numerical application of the aforementioned equation in a conventional mechanical watch balance wheel is shown, with the following characteristics:

[0073] - balance wheel outer radius = 5.3 mm;

[0074] - rotation at R = 4 mm;

[0075] - balance wheel inertia without inertial mass: 2 e-9 kg*m 2 ;

[0076] - mass of the inertial mass: 1.2 < m < 2.4 mg;

[0077] - target range + / - 15 seconds / day.

[0078] Figure 4 The graph in the figure shows on the y-axis the rate deviation AM in seconds / day and on the x-axis the symmetric radial movement value of the two inertial masses in microns, superimposed with the results obtained for four inertial mass mass values:

[0079] - curve C1 = 1.20 mg for m;

[0080] - curve C2 = 1.60 mg for m;

[0081] - curve C3 = 2.00 mg for m;

[0082] - curve C4 = 2.40 mg for m.

[0083] For example, the curve C2 associated with the inertial mass 3 of mass 1.6 mg corresponds to a glass parallelepiped of dimensions 0.30 x 1.33 x 1.70 mm 3 moved + / - 10 microns on either side of its zero position. The rate adjustment obtained here is + / - 11 seconds / day. This range can easily be extended by increasing the mass of the inertial mass or by increasing the peak-to-peak travel. Alternative embodiments include in particular the embedding of additional masses made of metal or any other specific material on this glass plate.

[0084] The choice of optomechanical actuator is essential to obtain reproducible precise results. The publication "Non-contact sub-nanometer optical repositioning with femtosecond lasers" by Y. Bellouard, Optics Express, November 2, 2015, Vol. 23, No. 22, as mentioned above, describes an ultra-high precision positioning device that can be used to align fiber optic axes, which requires positioning within a few nanometers. It comprises a demonstrator made of a glass wafer, of thickness of the order of 500 microns, commonly used for packaging and microfluidic applications.

[0085] Figure 5 The principle is schematically described: the support 2 carries fastenings 30, one of which carries an optomechanical actuator 35 itself, comprising two parallel arms 33 and 34, which are joined at the ends by a common segment 334, forming a U shape, the first arm 33 extending between the fastening 30 and the common segment, the second arm 34 extending between the common segment 334 and the exit point, here comprising non-limitatively a coupling neck 32 with a magnification mechanism 36. The other fastening 30 carries an inertial mass 3 connected by a neck 31, serving as a center of rotation.

[0086] Figure 2 、 Figure 3 and Figure 5 show particular alternative embodiments, for ease of implementation, each inertial mass 3 is mounted on the support 2 at its fastening 30.

[0087] Another alternative embodiment, see Figure 6 and Figures 9 to 12 in which the inertial mass 3 and the corresponding support 2 form a single-piece assembly, in particular a chip, which makes it possible to implement the inertial mass 3 and the support 2 on the same level, the support 2 then being constrained to the fastening zone 30 for fastening on the balance wheel 1.

[0088] Similarly, it can be further envisaged that the inertia block 3, the support 2 and the balance wheel 1 form a single piece assembly, although this alternative embodiment is more costly to produce.

[0089] According to the application, the first arm 33 and the second arm 34 are intended to receive laser pulses and each comprise a writing zone 391, 392 in which a very brief train of laser pulses emitted by the laser source 700 will produce a local modification of its structure by expansion of the molecules in the material thickness, this expansion being stopped quickly by stopping the pulses, the deformations thus remaining permanently deformed. These core deformations are extremely small, so that the method comprises locally juxtaposing a large number of expanded zones, so as to achieve sufficient cumulative expansion to move the inertia block 3 sufficiently along the rectilinear direction L. Advantageously, a mechanical amplifier 36, for example of the parallelogram type with four necks as shown, Figure 6 makes it possible to convert the total elongation or total retraction measurable at the exit point of the second arm 34 into a stroke of the inertia block 3, which is sufficient to significantly influence the rate of the pendulum 100.

[0090] It will be understood that the movement is different depending on whether the laser pulses etch the first arm 33 or the second arm 34: Figure 7 The case of the second writing zone 392, which is pulsed etched on the second arm 34, is shown, the overall movement of the exit point is then in the direction of the arrow B, in a pushing movement of the inertia block 3. Although Figure 8 The case of the first writing zone 391, which is pulsed etched on the first arm 33, is shown, but in a retraction movement of the inertia block 3, the overall movement of the exit point is then in the direction of the arrow A, opposite to the direction of the arrow B. Thus, it is possible to move the inertia block 3 radially in one direction or the other.

[0091] The action of the laser does not result in blanking, or even in surface etching, its purpose being to carry out a molecular reorganization on the core and thickness of the material. The concept of writing expansion lines is a reinterpretation of the application of a series of pulses according to a grid, the projection of the trajectory on the plane of the inertia block presenting as a series of very close parallel expansion lines, or very sharp zigzag expansion lines, or others; its purpose is in fact to expand the core material and to accumulate more closely the expansion along the same linear direction L.

[0092] By writing expansion lines in the material volume at the writing zones 39, in particular the first writing zone 391, the second writing zone 392, the material expands under the effect of a compressive stress in these zones. This state is caused by a very intense but sufficiently short isolated heating so as not to liquefy the material. The volume only expands very slightly, the material remaining solid. This isolated heating is performed using very short bursts of femtosecond laser, for example as described in the above-mentioned article "Non-contact sub-nanometer optical repositioning with femtosecond laser" by Y. Bellouard, Optics Express, November 2, 2015, Vol. 23, No. 22, but not limited thereto (Yb-fiber amplified laser, from Amplitude systèmes SA, wavelength = 1030 nm, pulse time 270 fs, pulse energy approximately 250 nJ, repetition frequency 800 kHz). The beam is focused by a lens at a point of a few microns, the working distance being of the order of 6 mm. The precision of these pulses therefore makes it possible to define one or more volume zones under stress by a three-dimensional scan with a precision of a few microns. Obviously, different femtosecond lasers (wavelength, pulse time, energy and repetition frequency) can be used, as long as they can modify the material as described above. The working distance of the focusing lens can vary depending on the laser beam shaping and focusing optics.

[0093] The non-limiting mechanism illustrated here, due to its very simplicity, Figures 5 to 8 comprises an "S" shaped actuator 35 along a radial linear direction L, arranged to act in two opposite directions along the same direction, whereby the writing occurs at the top zone of the second arm 34 (gain) or at the bottom zone of the first arm 33 (retraction). The amplifier 36 non-limitatively comprises a linkage system with a linkage 310 between the flexible necks 31, forming a linear guide along the linear direction L, and enabling to amplify the actuator with a multiplication factor Km, so that the embedded square stage, i.e. the inertia block 3, moves with an amplitude of a few microns.

[0094] According to the invention of the above-mentioned article (Y. Bellouard, 2015), for a block of 200 parallel planes written in a volume of total length of the order of 1 mm along the linear direction L, with the above-mentioned laser parameters and according to the figures, the following results are obtained: the multiplication coefficient Km is 6, the amplified travel of the inertia block 3 is of the order of 5 microns for 200 expansion lines written on a length of 1 mm; thus, for each written line, the appropriate movement at the actuator 35 along the linear direction L is equal to: 5 / (200*6) = 4.167 nm / line (or plane).

[0095] According to the above cited article, the same technique can be used to punch the microstructure itself. The first step consists in writing in a glass plate (fused silica) the volume zones to be removed according to the same core expansion method under laser irradiation. In a second step, the plate is chemically etched, selectively removing the stressed parts. The obtained machining is also accurate to the micron and makes it possible to produce glass microstructures.

[0096] Figure 9 and Figure 10 The application is shown in the above particular numerical example, the balance diameter is 10.6 mm (outer diameter of the rim 19); the diameter 190, here 8.0 mm, corresponds to the diameter of revolution of the mass center of the inertia block. The actuator 35 and the amplifier 36 are adapted to limit the planar dimensions of the support 2 to a square of side 2.0 mm, in particular a glass chip of thickness 0.3 mm, which carries the inertia block 3 and the support 2 on the same level, the support 2 being constrained to at least one fastening zone 30 for fastening the balance 1 and the suspension of the actuator 35, the amplifier 36 and the inertia block 3.

[0097] Thus, Figures 5 to 8 The mechanism schematically shown in Fig. 2 is modified for compactness and adaptation to the typical dimensions of a hairspring balance. We assume that, according to Hooke's law, the same stress σ applied to the actuator beam on a smaller cross section produces the same linear movement of 4.167 nm per line: dl / l = E*σ, where dl = length increase, l = zone length, E = Young's modulus of the material. In order to obtain the same amplitude as the previous actuator, the writing length of the 200 expansion lines must therefore be the same and equal to 1 mm along the linear direction L.

[0098] As Figure 9 shown in Fig. 3, for a glass support 2 of thickness 0.3 mm, the mass of the rectangular pallet stone forming the inertia block 3 is equal to 1.6 mg, corresponding to Figure 4 the rate-movement relationship C2 of the graph in Fig. 2.

[0099] In this example, the distance between the middle of the two deflection necks 31 defining the connecting rod 310 is 1.40 mm, and the distance between the lower deflection neck 31 and the middle of the coupling neck 32 is 0.14 mm. Here, the width of these deflection necks 31 or coupling necks 32 is 20 microns, which is acceptable from a technical point of view. According to the lever arm ratio, the multiplication factor Km between the actuator stroke and the mass stroke is equal to: Km = 1.400 mm / 0.140 mm = 10.

[0100] The maximum linear amplitude of this structure is equal to + / - x = Km * 200 expanded lines * 4.167 nm / line = 2000 * 4.167 nm = + / - 8.33 microns, which corresponds to approximately + / - delta ratio = + / - 9 seconds / day via the curve C2.

[0101] Thus, considering that there are 200 expanded lines for each of the two ranges of 9 seconds / day, the set resolution of each writing line is equal to d_rate (1 line) = 9 / 200 = 0.045 seconds / day per line, sufficient to adjust the rate in the range 0 to 2 seconds / day.

[0102] It should be noted that the two zones of 1 mm in length along the linear direction L make it possible to implement a single gain correction of + 9 seconds / day and a loss correction of - 9 seconds / day. In order to have several writing periods, it is possible to increase the number of supports 2 or to increase the mass, which has the effect of having to write fewer expanded lines for the same movement, and thus to reserve space on the first arm 33 and on the second arm 34 for subsequent writings.

[0103] As regards the implementation of the rate adjustment, the initial state is considered, in which, before the correction, the rate of the watch is assumed to be known and measurable, and the watch case is closed. To carry out the correction, it is necessary to use a specific fitting to precisely position the watch head. The microscope objective with cross movement xy and the positioning table then make it possible for the laser source 700, in particular a femtosecond layer, to be centred on the balance 1.

[0104] From this stage, two options arise: stopping the balance by locking / braking the bar, such as the seconds hand or similar device, or a mechanism for stopping and spatially holding the balance, laser irradiation on a fixed target, or the balance 1 continues to oscillate and the laser irradiation then has to be synchronised with its angular position.

[0105] The case of stopping the balance and laser irradiation on a fixed target can be solved by semi-automatic positioning, for example but not limited to by a control device managing a camera with image recognition software centred on the rotation axis D of the balance.

[0106] In the case where the balance 1 oscillates and the laser irradiation is synchronised with its angular position, the method is more complex but more advantageous, since the setting is carried out dynamically, without stopping the balance. As Figure 11 and Figure 12 shown, the irradiation can start as soon as the support 2 starts to pass through the detection laser beam 750.

[0107] Figure 11is a schematic cross-section through the rotation axis D of the balance 1, which shows the rim 19 of the balance 1, which carries the support 2, the inertia block 3 is not shown, the emission write laser source 700 for writing on the write zones 39, 391, 392, and the detection laser 750 obliquely mounted on the left part of the figure, in which the light beam reflected by the balance 1 and the elements comprised in it is collected on the right part of the figure by a collection device 760, such as a photodetector.

[0108] Figure 12 a detailed view of the arrangement according to Figure 11 , with the laser write source 700 and the laser detection source 750 for the case of oscillation of the balance 1, and in which the laser irradiation is synchronized with its angular position; the rim 19 of the balance 1 carries the chip according to Figure 9 ; the arcs represented in dotted line correspond to the instantaneous position of the laser write source 700, which irradiates perpendicularly to the plane of the figure, so that in this case it can write in the write zone 391 of the first lower arm 33, to produce an expansion line 390, i.e. a molecular expansion, indicated by the small arrows in this same zone 391, the adjacent small arrows corresponding to other expansion lines 390, i.e. writes already produced in the same zone with different positions along the x direction of the write source 700, corresponding to different light beams with respect to the rotation axis D of the balance 1. At the bottom part of the figure, from left to right, it can be seen the laser detection source 750, the converging lens 770, the incident light rays to the balance 1, the reflection points on the balance 1 or on the mechanism carried by it, the reflected light rays, the converging lens 780 and the photodetector 760.

[0109] In Figure 12 , the left edge of the rim 19 of the balance 1 oscillates from top to bottom in its circular trajectory. The chip 2 is fastened to the balance 1 by its bottom. The optics is composed of a laser write source 700, which performs an optical axis write in a direction z perpendicular to the plane of the balance 1, and a detection laser 750, for example inclined by an angle of 45° with respect to the balance plane, in which the axes of the incident and reflected light beams are in the plane xz. Their respective light points can be slightly offset along x, but must be kept on the same size along z.

[0110] Figure 13 Three time graphs are juxtaposed, on the x axis different time scales are plotted, but they are arranged in relation to each other to show specific times and the phenomena that occur: the top graph shows on the y axis the angular velocity omega OME of the balance 1, the middle graph shows on the y axis the signal VPD value of the photodetector 760, and the bottom graph shows on the y axis the light intensity IIE emitted by the laser write source 700.

[0111] When the balance 1 oscillates, its angular velocity omega OME is maximum near the neutral point, in Figure 13Between times t1 and t4 of the middle top graph, corresponding to the balance wheel with a few hertz of swing. This zone is interesting because the speed variation is not important, so it can be considered quasi-constant. Therefore, the detection laser 750 is used to turn on and off the write pulse train from the laser writing source 700.

[0112] As Figure 13 illustrated on the middle graph and Figure 12 , when the spot of the photodetector 760 associated with the detection laser 750 is located on the solid zone of the chip 2, i.e. successively on the fastening zone 30 / first lower arm 33 / second upper arm 34 / inertia block 3, its signal VPD has the value 1, while the signal VPD has the value 0 in the slot. Therefore, this signal can be used to write a pulse train by the laser writing source 700 between times t2 and t3, and more precisely in the first write zone 391 for a gain setting on the first arm 33, or in the second write zone 392 for a loss setting on the second arm 34. In the example illustrated in Figure 12 , four expansion lines 390 are written in the first gain zone on the first arm 33, which will pull the inertia block 3 towards the rotation axis D of the balance wheel 1 and induce a rate gain by increasing the frequency. The start of the light intensity IIE pulse train is triggered by the positive edge of the signal VPD at time TON, while its stop is triggered by the negative edge of the signal VPD at time TOFF. For example, an alternation, i.e. a half period, can be used to write an expansion line 390, then offset by an increment x with the laser writing source 700 to write the next adjacent expansion line in the next alternation, etc. The detection of the rotation direction is performed using the signal VPD, whose pattern differs according to the direction. This makes it possible to always turn on the laser writing source 700 in the correct zone.

[0113] The (passing through) writing duration Te in the first gain zone on the first arm 33 or in the second loss zone on the second arm 34 (zone of length Le) is given by:

[0114] - with R = radius of gyration, A = angular amplitude of the balance wheel, F = frequency of the swing.

[0115] In this example, Le = 190 um, R = 4 mm, A = 270°, F = 4 Hz, so Te = 0.40 ms.

[0116] In this example, the repetition frequency of the writing pulses is 800 kHz, so the number of pulses per pass is equal to 800 * 0.40 = 320, so the maximum (cumulated) gain error is equal to: 1 / 320 * (+ / - 9 s / day) = + / - 0.03 s / day, which is perfectly satisfactory for the application.

[0117] Femtosecond laser and chemical etching glass processing technology can produce three-dimensional structures with micron precision, which is a well-proven technology.

[0118] This technology can produce two millimeter-scale chips with flexible elements that can move in micrometer-scale amplitude with nanometer-scale precision. The actuation of the nanometer movement of the actuator part 35 is performed by laser internal stress writing. The system of flexible neck 31 and connecting rod 310 makes it possible to increase the amplitude along the linear direction l.

[0119] Embodiments of such a chip 2 are suitable for precisely and reliably setting the rate of a hairspring balance, with a precision of 0.03 seconds / day and a resolution of 0.09 seconds / day, and a range typically of + / - 10 seconds / day. Obviously, by adjusting the design, it is possible to easily change the range amplitude and resolution.

[0120] It can be noted that the present invention offers the possibility of making infinitesimal and irreversible expansions, which, in theory, can change the stiffness of the elastic return element of the balance, such as a spiral spring, a flexible band or the like, by a series of irradiations thereon; however, the creation of these deformation zones hinders the uniformity of the component and there is a risk that the elastic properties of the elastic return element are compromised. For this reason, the present invention is preferably used here for the action on the inertial element, regardless of whether it is suspended by a spiral spring or by a flexible band.

[0121] The setting system is compact in structure, and does not require additional complex components to be installed in the watch 1000, in addition to the two or more glass chips 2 installed on the balance 1.

[0122] This setting can be made directly on the complete watch 1000, provided that the watch head 500 comprises a transmissive transparent element 600, such as the watch back, the watch glass or other element, which is transparent or non-absorbing to the writing laser in optical access on the balance. The present invention naturally relates to a watch 1000 thus equipped.

[0123] Figure 14 The peripheral devices and their links are shown: control device 790, cross-moving stage 710 for operating the writing laser 700, detection laser 750, device 760 for collecting reflected light rays, and device 720 for starting and stopping the balance 100.

[0124] The external part of the setting (accessories, microscope, optics and lasers) usually occupies the volume of a table, which makes it possible to have a quick and user-friendly setting in production and in-store customer service.

[0125] The implementation of the invention is even more superior due to the optimization of the absorption of light rays by the physical protection isolation (shell, cover), due to the implementation of a reliable system for positioning the laser point. Naturally, the appropriate dimensions should be used for the live zones, exceeding certain experimentally determined dimensions, in order to prevent the increase in the fragility of these live zones, which can lead to premature rupture during impact.

Claims

1. A method for precisely adjusting the rate of a mechanical clock oscillator (100), said oscillator comprising at least one inertial mass (1) arranged to oscillate about a rotation axis (D) and return to a stationary position via an elastic return device, characterized in that, In the first step (801), the oscillator (100) is equipped with at least one inertial mass block (1), the inertial mass block including an actuator (35), the actuator (35) being made of a material suitable for irreversible local micro-expansion under laser irradiation, the actuator (35) being arranged to impart a radial linear travel of the inertial mass block (3) relative to the axis of rotation (D) directly or via at least one amplification mechanism (36) when the writing area (39; 391; 392) included in the actuator (35) is subjected to suitable laser irradiation; in the second step (802), a first coarse setting of the initial rate of the oscillator (100) is performed within a first rate range, and the rate is measured; in the third step (803), the calculation of the amount to be imparted is... The direction and value of the rate deviation of the oscillator (100) are determined to bring it into a predetermined second rate range, and the direction and value of the stroke to be given to each of the inertial blocks (3) included in the oscillator (100) are calculated. In the fourth step (804), at least one of the writing regions (39; 391; 392) is subjected to femtosecond laser irradiation to generate at least one expansion line (390) through local molecular expansion of the material, thereby causing the actuator (35) to deform radially relative to the axis of rotation (D). In the fifth step (805), the rate of the oscillator (100) is measured, and the third step (803) and the fourth step (804) are repeated until the rate of the oscillator (100) is within the second rate range.

2. The method according to claim 1, characterized in that, The method is applied to the oscillator (100) having at least two of the inertial mass blocks (1), each of the inertial mass blocks including the actuator (35).

3. The method according to claim 1 or 2, characterized in that, During the fourth step (804), a femtosecond laser source (700) is used, which is mounted on a stage with cross motion (710) or radial travel, so as to juxtapose different series of irradiations on different beams relative to the axis of rotation (D), thereby generating a series of expansion lines (390) in close proximity to each other.

4. The method according to claim 1 or 2, characterized in that, During the fourth step (804), a femtosecond laser source (700) is used to perform laser irradiation in each rotational direction of the inertial mass block (1).

5. The method according to claim 1 or 2, characterized in that, During the fourth step (804), the control device (790) controls the irradiation of the femtosecond laser source (700) based on information about the presence or absence of material provided by a combination of the detection laser (750) and the collection device (760) or the photodetector.

6. The method according to claim 1 or 2, characterized in that, During the first step (801), the actuator (35) is selected to include a first write area (391) on the first arm (33) and a second write area (392) on the second arm (34), the second arm (34) being parallel to the first arm (33) along a radial linear direction (L) and connected to it at a common segment (334), the actuator (35) thus being mounted in an "S" shape on one side, fastened to a support (2) mounted on the inertial mass block (1) or directly fastened to the inertial mass. Between the fastening area (30) of the gauge block (1) and, on the other hand, the exit point or coupling neck (32) for connection with the amplification mechanism (36), the actuator (35) is arranged to act in two opposite directions along the linear direction (L), so that during the fourth step (804), for gain setting, femtosecond laser irradiation writing occurs in the first writing area (391) on the first arm (33), or for loss setting, it occurs in the second writing area (392) on the second arm (34).

7. The method according to claim 1 or 2, characterized in that, During the first step (801), the actuator (35) is selected to have an exit point or coupling neck (32) for coupling with an amplification mechanism (36) arranged to amplify the exit stroke of the actuator (35) to impart the amplified stroke to the inertial block (3).

8. The method according to claim 7, characterized in that, The amplification mechanism (36) is of the parallelogram type and includes a linkage system having links (310) arranged between flexible necks (31) to form a linear guide along a radial linear direction (L).

9. The method according to claim 1 or 2, characterized in that, During the first step (801), the actuator (35) is selected to include a fastening area (30) that is rigidly connected to a support (2) mounted on the inertial mass block (1), and wherein the support (2) forms a single-piece assembly that forms a flexible micromechanism, wherein the actuator (35), the amplification mechanism (36) and the inertial mass block (3) are mounted in series with each other.

10. The method according to claim 1 or 2, characterized in that, During the first step (801), the actuator (35) is selected to include a fastener (2) fastened to a support (2) mounted on the inertial mass block (1) or a fastening area (30) rigidly connected to the support (2), wherein the actuator (35) and / or the support (2) are made of glass.

11. The method according to claim 1 or 2, characterized in that, During the first step (801), the inertial mass block (1) is selected in the form of a balance wheel, which includes at least a pair of identical inertial blocks (3) that are radially opposite to the axis of rotation (D).

12. The method according to claim 1 or 2, characterized in that, During the first step (801), the oscillator (100) is incorporated into the head (500) of the watch (1000), the head (500) including at least one transmissive transparent element (600) that separates the exterior and interior of the watch (1000) and allows at least one laser to optically access at least the inertial mass block (1) of the oscillator (100) of the watch.

13. The method according to claim 1 or 2, characterized in that, During the first step (801), the oscillator (100) is equipped with a stop or second hand device arranged to apply pressure to the inertial mass block (1), and wherein the fourth step (804) is performed in the locked position of the inertial mass block (1).

14. The method according to any one of claims 1 or 2, characterized in that, During the fourth step (804), the femtosecond laser writing irradiation is performed during the oscillation of the inertial mass block (1), wherein the angular position and the irradiation are synchronized.

15. The method according to any one of claims 1 or 2, characterized in that, During the fourth step (804), the irradiation is performed using a femtosecond laser.

16. The method according to claim 15, characterized in that, During the fourth step (804), the irradiation is performed using a femtosecond laser with a wavelength between 900 nm and 1100 nm, a pulse duration between 200 fs and 350 fs, a pulse energy between 200 nJ and 300 nJ, and a repetition frequency between 700 kHz and 900 kHz.

17. A mechanical clock pendulum (100) comprising at least one inertial mass (1) arranged to oscillate about a rotation axis (D) and return to a stationary position via an elastic return device, characterized in that, At least one of the inertial mass blocks (1) includes an actuator (35) made of a material suitable for irreversible local micro-expansion under laser irradiation, the actuator (35) being arranged to impart radial linear travel of the inertial mass block (3) relative to the axis of rotation (D) directly or via at least one amplification mechanism (36) when the write regions (39; 391; 392) included in the actuator (35) are subjected to suitable laser irradiation.

18. The mechanical clock oscillator (100) according to claim 17, characterized in that, The actuator (35) includes a first write area (391) on a first arm (33) and a second write area (392) on a second arm (34) which is parallel to the first arm (33) along a radial linear direction (L) and connected to it at a common segment (334). The actuator (35) is thus mounted in an "S" shape on one side, fastened to a support (2) mounted on the inertial mass block (1) or directly fastened to a fastening area (30) of the inertial mass block (1), and on the other side, between an exit point or a coupling neck (32) for connection with the amplification mechanism (36). The actuator (35) is arranged to act in two opposite directions along the linear direction (L), whereby, for a gain setting, femtosecond laser irradiation is applied to the first write area (391) on the first arm (33), or for a loss setting, it is applied to the second write area (392) on the second arm (34).

19. The mechanical clock oscillator (100) according to claim 17 or 18, characterized in that, The actuator (35) includes an exit point of a coupling neck (32) for coupling with an amplification mechanism (36) arranged to amplify the stroke of the actuator (35) to impart the amplified stroke to the inertial block (3), and wherein the amplification mechanism (36) is of the parallelogram type and includes a linkage system having links (310) arranged between flexible necks (31) to form a linear guide along a radial linear direction (L).

20. The mechanical clock oscillator (100) according to claim 17 or 18, characterized in that, The actuator (35) includes a fastening area (30) which is rigidly connected to a support (2) mounted on the inertial mass block (1), and wherein the support (2) forms a single component that forms a flexible micromechanism, wherein the actuator (35), the amplification mechanism (36) and the inertial mass block (3) are mounted in series with each other.

21. The mechanical clock oscillator (100) according to claim 17 or 18, characterized in that, The actuator (35) includes a fastener (2) fastened to a support (2) mounted on the inertial mass block (1) or a fastening area (30) rigidly connected to the support (2), wherein the actuator (35) and / or the support (2) are made of glass.

22. The mechanical clock oscillator (100) according to claim 17 or 18, characterized in that, The inertial mass block (1) is a balance wheel, which includes at least one pair of identical inertial blocks (3) that are radially opposite to the axis of rotation (D).

23. A watch (1000) comprising at least one mechanical clockwork oscillator (100) according to any one of claims 17 to 22, characterized in that, The table (1000) includes a head (500) that includes at least one transmissive transparent element (600) that separates the exterior and interior of the table (1000) and allows at least one laser to optically access at least the inertial mass block (1) of the oscillator (100) of the table.

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